diff options
| -rw-r--r-- | media/libstagefright/MPEG4Writer.cpp | 198 |
1 files changed, 1 insertions, 197 deletions
diff --git a/media/libstagefright/MPEG4Writer.cpp b/media/libstagefright/MPEG4Writer.cpp index 58f6699..ea9911c 100644 --- a/media/libstagefright/MPEG4Writer.cpp +++ b/media/libstagefright/MPEG4Writer.cpp @@ -47,10 +47,6 @@ static const uint8_t kNalUnitTypeSeqParamSet = 0x07; static const uint8_t kNalUnitTypePicParamSet = 0x08; static const int64_t kInitialDelayTimeUs = 700000LL; -// Using longer adjustment period to suppress fluctuations in -// the audio encoding paths -static const int64_t kVideoMediaTimeAdjustPeriodTimeUs = 600000000LL; // 10 minutes - class MPEG4Writer::Track { public: Track(MPEG4Writer *owner, const sp<MediaSource> &source, size_t trackId); @@ -88,8 +84,6 @@ private: int64_t mTrackDurationUs; int64_t mMaxChunkDurationUs; - // For realtime applications, we need to adjust the media clock - // for video track based on the audio media clock bool mIsRealTimeRecording; int64_t mMaxTimeStampUs; int64_t mEstimatedTrackSizeBytes; @@ -175,28 +169,9 @@ private: int64_t mPreviousTrackTimeUs; int64_t mTrackEveryTimeDurationUs; - // Has the media time adjustment for video started? - bool mIsMediaTimeAdjustmentOn; - // The time stamp when previous media time adjustment period starts - int64_t mPrevMediaTimeAdjustTimestampUs; - // Number of vidoe frames whose time stamp may be adjusted - int64_t mMediaTimeAdjustNumFrames; - // The sample number when previous meida time adjustmnet period starts - int64_t mPrevMediaTimeAdjustSample; - // The total accumulated drift time within a period of - // kVideoMediaTimeAdjustPeriodTimeUs. - int64_t mTotalDriftTimeToAdjustUs; - // The total accumalated drift time since the start of the recording - // excluding the current time adjustment period - int64_t mPrevTotalAccumDriftTimeUs; - // Update the audio track's drift information. void updateDriftTime(const sp<MetaData>& meta); - // Adjust the time stamp of the video track according to - // the drift time information from the audio track. - void adjustMediaTime(int64_t *timestampUs); - static void *ThreadWrapper(void *me); status_t threadEntry(); @@ -1512,12 +1487,7 @@ status_t MPEG4Writer::Track::start(MetaData *params) { mNumSttsTableEntries = 0; mNumCttsTableEntries = 0; mMdatSizeBytes = 0; - mIsMediaTimeAdjustmentOn = false; - mPrevMediaTimeAdjustTimestampUs = 0; - mMediaTimeAdjustNumFrames = 0; - mPrevMediaTimeAdjustSample = 0; - mTotalDriftTimeToAdjustUs = 0; - mPrevTotalAccumDriftTimeUs = 0; + mMaxChunkDurationUs = 0; mHasNegativeCttsDeltaDuration = false; @@ -1816,128 +1786,6 @@ status_t MPEG4Writer::Track::makeAVCCodecSpecificData( } /* -* The video track's media time adjustment for real-time applications -* is described as follows: -* -* First, the media time adjustment is done for every period of -* kVideoMediaTimeAdjustPeriodTimeUs. kVideoMediaTimeAdjustPeriodTimeUs -* is currently a fixed value chosen heuristically. The value of -* kVideoMediaTimeAdjustPeriodTimeUs should not be very large or very small -* for two considerations: on one hand, a relatively large value -* helps reduce large fluctuation of drift time in the audio encoding -* path; while on the other hand, a relatively small value helps keep -* restoring synchronization in audio/video more frequently. Note for the -* very first period of kVideoMediaTimeAdjustPeriodTimeUs, there is -* no media time adjustment for the video track. -* -* Second, the total accumulated audio track time drift found -* in a period of kVideoMediaTimeAdjustPeriodTimeUs is distributed -* over a stream of incoming video frames. The number of video frames -* affected is determined based on the number of recorded video frames -* within the past kVideoMediaTimeAdjustPeriodTimeUs period. -* We choose to distribute the drift time over only a portion -* (rather than all) of the total number of recorded video frames -* in order to make sure that the video track media time adjustment is -* completed for the current period before the next video track media -* time adjustment period starts. Currently, the portion chosen is a -* half (0.5). -* -* Last, various additional checks are performed to ensure that -* the actual audio encoding path does not have too much drift. -* In particular, 1) we want to limit the average incremental time -* adjustment for each video frame to be less than a threshold -* for a single period of kVideoMediaTimeAdjustPeriodTimeUs. -* Currently, the threshold is set to 5 ms. If the average incremental -* media time adjustment for a video frame is larger than the -* threshold, the audio encoding path has too much time drift. -* 2) We also want to limit the total time drift in the audio -* encoding path to be less than a threshold for a period of -* kVideoMediaTimeAdjustPeriodTimeUs. Currently, the threshold -* is 0.5% of kVideoMediaTimeAdjustPeriodTimeUs. If the time drift of -* the audio encoding path is larger than the threshold, the audio -* encoding path has too much time drift. We treat the large time -* drift of the audio encoding path as errors, since there is no -* way to keep audio/video in synchronization for real-time -* applications if the time drift is too large unless we drop some -* video frames, which has its own problems that we don't want -* to get into for the time being. -*/ -void MPEG4Writer::Track::adjustMediaTime(int64_t *timestampUs) { - if (*timestampUs - mPrevMediaTimeAdjustTimestampUs >= - kVideoMediaTimeAdjustPeriodTimeUs) { - - LOGV("New media time adjustment period at %lld us", *timestampUs); - mIsMediaTimeAdjustmentOn = true; - mMediaTimeAdjustNumFrames = - (mNumSamples - mPrevMediaTimeAdjustSample) >> 1; - - mPrevMediaTimeAdjustTimestampUs = *timestampUs; - mPrevMediaTimeAdjustSample = mNumSamples; - int64_t totalAccumDriftTimeUs = mOwner->getDriftTimeUs(); - mTotalDriftTimeToAdjustUs = - totalAccumDriftTimeUs - mPrevTotalAccumDriftTimeUs; - - mPrevTotalAccumDriftTimeUs = totalAccumDriftTimeUs; - - // Check on incremental adjusted time per frame - int64_t adjustTimePerFrameUs = - mTotalDriftTimeToAdjustUs / mMediaTimeAdjustNumFrames; - - if (adjustTimePerFrameUs < 0) { - adjustTimePerFrameUs = -adjustTimePerFrameUs; - } - if (adjustTimePerFrameUs >= 5000) { - LOGE("Adjusted time per video frame is %lld us", - adjustTimePerFrameUs); - CHECK(!"Video frame time adjustment is too large!"); - } - - // Check on total accumulated time drift within a period of - // kVideoMediaTimeAdjustPeriodTimeUs. - int64_t driftPercentage = (mTotalDriftTimeToAdjustUs * 1000) - / kVideoMediaTimeAdjustPeriodTimeUs; - - if (driftPercentage < 0) { - driftPercentage = -driftPercentage; - } - if (driftPercentage > 5) { - LOGE("Audio track has time drift %lld us over %lld us", - mTotalDriftTimeToAdjustUs, - kVideoMediaTimeAdjustPeriodTimeUs); - - CHECK(!"The audio track media time drifts too much!"); - } - - } - - if (mIsMediaTimeAdjustmentOn) { - if (mNumSamples - mPrevMediaTimeAdjustSample <= - mMediaTimeAdjustNumFrames) { - - // Do media time incremental adjustment - int64_t incrementalAdjustTimeUs = - (mTotalDriftTimeToAdjustUs * - (mNumSamples - mPrevMediaTimeAdjustSample)) - / mMediaTimeAdjustNumFrames; - - *timestampUs += - (incrementalAdjustTimeUs + mPrevTotalAccumDriftTimeUs); - - LOGV("Incremental video frame media time adjustment: %lld us", - (incrementalAdjustTimeUs + mPrevTotalAccumDriftTimeUs)); - } else { - // Within the remaining adjustment period, - // no incremental adjustment is needed. - *timestampUs += - (mTotalDriftTimeToAdjustUs + mPrevTotalAccumDriftTimeUs); - - LOGV("Fixed video frame media time adjustment: %lld us", - (mTotalDriftTimeToAdjustUs + mPrevTotalAccumDriftTimeUs)); - } - } -} - -/* * Updates the drift time from the audio track so that * the video track can get the updated drift time information * from the file writer. The fluctuation of the drift time of the audio @@ -2080,32 +1928,6 @@ status_t MPEG4Writer::Track::threadEntry() { int32_t isSync = false; meta_data->findInt32(kKeyIsSyncFrame, &isSync); - - /* - * The original timestamp found in the data buffer will be modified as below: - * - * There is a playback offset into this track if the track's start time - * is not the same as the movie start time, which will be recorded in edst - * box of the output file. The playback offset is to make sure that the - * starting time of the audio/video tracks are synchronized. Although the - * track's media timestamp may be subject to various modifications - * as outlined below, the track's playback offset time remains unchanged - * once the first data buffer of the track is received. - * - * The media time stamp will be calculated by subtracting the playback offset - * (and potential pause durations) from the original timestamp in the buffer. - * - * If this track is a video track for a real-time recording application with - * both audio and video tracks, its media timestamp will subject to further - * modification based on the media clock of the audio track. This modification - * is needed for the purpose of maintaining good audio/video synchronization. - * - * If the recording session is paused and resumed multiple times, the track - * media timestamp will be modified as if the recording session had never been - * paused at all during playback of the recorded output file. In other words, - * the output file will have no memory of pause/resume durations. - * - */ CHECK(meta_data->findInt64(kKeyTime, ×tampUs)); //////////////////////////////////////////////////////////////////////////////// @@ -2146,31 +1968,13 @@ status_t MPEG4Writer::Track::threadEntry() { timestampUs, cttsDeltaTimeUs); } - // Media time adjustment for real-time applications if (mIsRealTimeRecording) { if (mIsAudio) { updateDriftTime(meta_data); - } else { - adjustMediaTime(×tampUs); } } CHECK(timestampUs >= 0); - if (mNumSamples > 1) { - if (timestampUs <= lastTimestampUs) { - LOGW("Frame arrives too late!"); - // Don't drop the late frame, since dropping a frame may cause - // problems later during playback - - // The idea here is to avoid having two or more samples with the - // same timestamp in the output file. - if (mTimeScale >= 1000000LL) { - timestampUs = lastTimestampUs + 1; - } else { - timestampUs = lastTimestampUs + (1000000LL + (mTimeScale >> 1)) / mTimeScale; - } - } - } LOGV("%s media time stamp: %lld and previous paused duration %lld", mIsAudio? "Audio": "Video", timestampUs, previousPausedDurationUs); |